Cooling device for an internal combustion engine

ABSTRACT

A cooling device is proposed that can be produced by the diecasting process, and which has a heat-transfer unit surrounded by an outer shell, wherein a jacket through which coolant flows is formed between the heat-transfer unit and the outer shell, said jacket is subdivided by webs in such a way that a passage through which coolant flows is formed between the outer shell and the outer casing of the heat-transfer unit. To this end, the webs are arranged in such a way that this circulating flow is effected in a meander shape. Compared with a spiral flow, this results in degrees of freedom with regard to the arrangement of the coolant inlets and coolant outlets. Furthermore, such cooling devices can be produced and assembled in a cost-effective manner and have a high efficiency.

The invention refers to a cooling device, in particular an exhaust gas cooling device, for an internal combustion engine, with an outer shell in which at least one heat transfer unit is arranged that has an outer casing separating a jacket, formed between the outer shell and the heat transfer unit and through which coolant flows, from a passage formed in the heat transfer unit and through which the fluid to be cooled flows, with webs being provided between the outer shell and the outer casing of the heat transfer unit that define channels in the shell through which coolant flows.

Such cooling devices are used, for example, in internal combustion engines as exhaust gas cooling devices to reduce pollutant emission by cooling the exhaust gas, mixing it with the air freshly taken in and supplying it to the cylinders. By this decrease of the temperature of the cylinder filling, the emission of pollutants is reduced. To achieve this, very different embodiments of cooling devices have been applied for.

A problem with many of these cooling devices are dead spaces or turbulences in the jacket through which coolant flows, where no coolant exchange occurs, whereby the efficiency of the cooling device is significantly reduced. Further, damage could be done to the cooling device should the coolant seethe.

To avoid such dead water spaces and to increase the efficiency of the heat exchanger, cooling devices have been developed that include a positive flow of the coolant.

DE 20 48 474, for example, discloses a partition wall for a cooling device that is located in the coolant casing and defines a flow-through channel. This cooling device is cylindrical, the webs for the positive flow of the coolant flow being formed by a separating blade provided subsequently on the inner heat transfer unit, said blade surrounding the inner heat transfer unit helically so that a spiral positive flow about the heat transfer unit is achieved.

A similar embodiment is also known from DE 20 2004 008 737 which also discloses a cylindrical heat transfer unit, whose partition walls are spirally, i.e. helically, arranged around the inner passage. These partition walls are formed by a wire that is almost square in shape. This wire is subsequently materially fastened to the inner pipe, i.e. the heat transfer unit.

A cylindrical oil cooler with webs for the positive flow of the coolant is known from U.S. Pat. No. 1,983,466, which webs do not extend fully around the circumference, respectively, wherein discontinuities in the webs are provided in alternate order on opposite sides so that the coolant can flow to the opposite side in both circumferential directions.

Further, a heat exchanger is known from U.S. Pat. No. 2,796,239 through which coolant flows on one side, with webs being formed on the partition wall between the two media or at the cover part of the cooling channel, which cause a meandering positive flow.

It is a drawback of such embodiments that, with such helical positive flows, the heat exchanger is fixed with respect to the positioning of the coolant inlet and outlet. With a helical flow circulating around the inner heat transfer unit, the inlets and outlets for the coolant have to be situated at the axial ends of the heat exchanger.

Furthermore, it is disadvantageous that it is only very difficult and complex under aspects of manufacturing to make the inner heat transfer unit not cylindrical, but parallelepiped or of several parts, for example, or to arrange a plurality of heat transfer units in a outer shell, with a positive circulating flow possibly flowing around each heat transfer unit completely. In such a case, it would be necessary to be able to exactly associate the respective helical extensions of the webs defining the passages in both parts so that no clefts or gaps exist between the individual parts.

It is thus the object of the invention to provide a cooling device with a positive coolant flow, which has high degrees of freedom with respect to the arrangement of coolant inlets and outlets, while simultaneously allowing the inner heat transfer unit to be readily made from multiple parts. Moreover, it is also intended to be possible, for example, to arrange a plurality of heat transfer units in a housing around which a positive circulating flow still flows as completely as possible.

This object is solved by making the heat transfer device in a diecasting process and by forming it from an upper part and a lid-shaped lower part, which parts are connected by welding, especially by friction stir welding, the webs defining the passage through which the coolant flows being arranged such that a positive circulating flow passes through the heat transfer unit in a meandering shape. This meander-shaped flow allows for a free choice of the positions of the inlets and outlets, as well as of the shape of the cooling device and the heat transfer unit. Even with a multipart design of the heat transfer unit, the webs can be made with the heat transfer unit in a simple manner and without offset. Using aluminum or magnesium diecasting, the heat transfer unit can be made lightweight, yet at low cost. At the same time it is also suited for high temperatures. Friction stir welding is particularly well suited for used with magnesium or aluminum diecast coolers. Additional protrusions or eyelets for screw connections, as they are known from other cooling devices for the connection of two parts, are not needed here, so that a very compact and still tight assembly without additional seals is guaranteed.

In a preferred embodiment, a first axial web is provided between the outer shell and the outer casing of the heat transfer unit, from which web circumferential webs alternately extend from both sides of the axial web and around the heat transfer unit, the circumferential webs ending a distance shy of the axial web that preferably corresponds to the distance between the circumferential webs. In such an arrangement, there are only webs that are perpendicular to each other, which webs can be arranged in a simple and precise manner with respect to each other even in a multipart heat transfer unit, so that dead spaces are completely avoided. In such a cooling device, the coolant inlet is arranged at the first axial end of the cooling device, while the coolant outlet is located at the opposite axial end. Along the circumference, a full positive circulating flow exists around the heat transfer unit and thus a high efficiency.

In an embodiment alternative thereto, two opposing axial webs are formed between the outer shell and the outer casing of the heat transfer unit, a first web thereof ending shy of a last axial section of the cooling device, and from which webs circumferential webs extend alternately from the first axial web and the second axial web to both sides of the respective axial web and around the heat transfer unit, the circumferential webs ending a distance shy of the respective other axial web that corresponds to the distance between the circumferential webs. With such an embodiment, the coolant inlet and the coolant outlet can be located at the same axial end of the cooling device so that the cooling device is flown around in meander-like manner first in its first half and then in its second half. In such an embodiment, the flow through the heat transfer unit can be chosen to be correspondingly unshaped, so that the cooling device can be operated both in counter flow and in parallel flow. The relative arrangement of the webs remains simple to realize and dead spaces are still avoided.

In a further alternative embodiment, two transfer units are arranged in an outer shell, with webs formed between them such that, in cross section, each of the transfer units is passed on all sides by a positive circulating flow. Such a case pertains to a two-stage cooler having the advantage of a more compact axial length so that also in this case clearly higher degrees of freedom exist when compared with coolers with a helical positive circulating flow therethrough.

Such a flow on all sides is achieved by the two heat transfer units being passed substantially in the shape of an eight, seen in cross section. Additional forward and backward flows are thus avoided, and coolant inlet and outlet channels can be arranged on the axially opposite sides heat transfer unit.

In such a preferred embodiment, a respective axial web is provided between the outer shell and each of the two heat transfer units, the two axial webs being arranged on opposite circumferential sides of the shell and circumferentially extending webs alternately running from both sides of the axial webs and around the heat transfer units, each circumferential web ending a distance shy of the first axial web and each second circumferential web ending a distance shy of the second axial web. In a particularly simple manner, such an embodiment guarantees a circulating flow around the two-stage heat exchanger in the shape of an eight.

Preferably, the webs are at least partly arranged at the outer casing of the heat transfer unit, so that no additional inserts are needed to allow a functioning positive circulating flow. In the diecasting process, these webs can then be produced in only a single step together with the heat transfer unit.

In an advanced or alternative embodiment, the outer shell is made of at least two parts and is manufactured by diecasting, the webs being formed at least in part on an inner wall of the outer shell. Of course, also in such an embodiment, the webs may be formed entirely on the outer shell and extend to the outer wall of the heat transfer unit. Intermediate solutions are also conceivable, where the webs are formed in part on the outer casing of the heat transfer unit and in part on the inner wall of a bipartite outer shell. In both instances, additional inserts and thus manufacturing steps are avoided.

In an embodiment continuative to the above, the webs are substantially formed on the outer casing of the heat transfer unit and are provided with discontinuities in the junction between the upper part and the lower part, which, in the assembled state, are filled by corresponding webs of the outer shell.

Such an embodiment is particularly useful with multipart heat transfer units that are afterwards welded. Typically, this requires a cutout in the region between the components of the heat transfer unit in order to allow the application of the corresponding welding tool. In order to still prevent an overflow of coolant at these locations in the assembled state, they may intentionally be recessed in the heat transfer unit and be filled again in the assembled state by corresponding webs on the inner wall of the outer shell, so that no regions with stagnant coolant exist.

In an embodiment alternative thereto, the webs in the junction between the upper part and the lower part of the heat transfer unit are formed so as to extend continuously, seen in cross section. This may result in minor pressure losses in the coolant casing since the cross section is no longer equal over the entire extension, however, such an embodiment allows to pass a welding tool across the webs formed continuously in this region, without destroying the reliable separation of the channels by the webs.

The cooling devices claimed have a high efficiency, while their structural size and the arrangement of the coolant inlets and outlets can be chosen almost freely. Such cooling devices are simple and economical to manufacture and assemble, without having to use additional components.

Three embodiments are illustrated in the drawings and will be detailed hereinafter.

FIG. 1 is a top plan view of a heat transfer unit of a cooling device according to the present invention.

FIG. 2 is a side elevational view of the heat transfer unit of FIG. 1.

FIG. 3 is a bottom view of the heat transfer unit of FIGS. 1 and 2.

FIG. 4 is a bottom view of an alternative cooling device with a two-stage outer casing, a part of the outer shell being cut away.

FIG. 5 is a sectional view of a front view of the cooling device of FIG. 4.

FIG. 6 illustrates a third embodiment of a cooling device according to the present invention in a partly sectional top plan view.

FIGS. 1 to 3 illustrate a heat transfer unit 1 of a cooling device typically enclosed by a one-piece outer shell, not illustrated. The heat transfer unit 1 has an outer casing 2 at which webs 3, 4, 5, 6 are formed. These webs 3, 4, 5, 6 serve to provide a positive circulating flow around the heat transfer unit 1. Their height corresponds to the distance between an inner wall of the outer shell and the outer casing 2 of the heat transfer unit 1, so that a jacket formed between the outer shell, not illustrated, and the heat transfer unit 1 is divided into a continuously extending passage 7 by the webs 3, 4, 5, 6.

Inside the heat transfer unit 1 a passage is formed through which exhaust gas flows and in which ribs may be provided, for example, for better heat transfer. In the present embodiment, the heat transfer unit 1 is U-shaped, i.e. at least one axial web is formed within the heat transfer unit 1, which is interrupted in the rear portion, thereby allowing a deflection of the exhaust gas flow. Correspondingly, an exhaust gas inlet 8 and an exhaust gas outlet 9 are formed at the same axial end of the heat transfer unit 1.

To be able to pass the coolant flow along the heat transfer unit 1, substantially either against the exhaust flow or with the exhaust flow, the webs 3, 4, 5, 6 are configured such that the heat transfer unit 1 is traversed by a positive circulating flow in a meandering manner first in its first half 10 and then, in the reverse direction, in its second half 11, so that a coolant inlet 12 and a coolant outlet are located at the same axial end of the heat transfer unit 1.

For this purpose, the outer casing 2 of the heat transfer unit 1 is provided with two axial webs 3, 4, a first axial web 3 being located on the upper side illustrated in FIG. 1 and a second axial web 4 being located on the lower side of the heat transfer unit 1 illustrated in FIG. 2. From these axial webs 3, 4, webs 5, 6 extend alternately in the circumferential direction on either side of the webs 3, 4, seen in the axial direction, which each end shy of the axial web 4, 3 located on the opposite side. The distance between the end of a circumferential web 5, 6 and the respective concerned axial web 3, 4 substantially corresponds to the distance between two successive circumferential webs 5, 6, so that only little pressure loss exists.

From FIGS. 1 to 3, the coolant path is now evident. Through the coolant inlet 12, the coolant flows in the direction of the axial web 3 visible in FIG. 1 and, between the end of the circumferential web 8 and the axial web 3, it flows between the two circumferential webs 5, 6. From there, the coolant flows along the side wall illustrated in FIG. 2 to the lower side of the heat transfer unit 1, illustrated in FIG. 3. here, the flow is again deflected into the axial direction, so that the coolant is again deflected by 90° between the end of the circumferential web 5 and the axial web 4 and can flow back to the upper side between the webs 5, 6. This meandering movement is carried on with repeated deflection up to the other axial end of the heat transfer unit 1, where the coolant can flow on the upper side of the heat transfer unit 1, shown in FIG. 1, to the opposite side wall of the heat transfer unit 1, since the axial web 3 is interrupted in this region. From there, the meandering movement goes on respectively about half the cross section of the heat transfer unit 1 to the outlet 13.

FIGS. 4 and 5 illustrate a similar cooling device, with an outer shell 14 being shown as well, which is open in FIG. 4. The inner walls of the outer shell 14 are formed with double webs 15 that embrace the webs 3, 4, 5, 6, so that a reliable sealing is achieved. To be able to achieve this, the outer shell is formed by an upper part 16 and a lower part 17, as is evident from FIG. 5.

As already obvious from FIGS. 1 to 3, the heat transfer unit 1 is also of bipartite structure with an upper part 18 and a cover-shaped lower part 19. The flow through the cooling device illustrated in FIGS. 4 and 5 is effected in the same manner as described with reference to FIGS. 1 and 3, with the present illustration also showing the jacket 20 and, in FIG. 5, the inner passage 21 through which exhaust gas flows, with ribs 22 extending into the passage 21 from both parts 18, 19. Further, a central rib 23 is illustrated that separates the first half 10, through which the flow passes first, from the second half 11 that is flown through in the opposite direction.

It is obvious from FIG. 4 that in the area of the outer edges of the cover-shaped lower part 19 of the heat transfer unit 1 the circumferential webs 5, 6 have discontinuities 24. These discontinuities 24 exist because the fastening of the lower part 19 to the upper part 18 includes a welding operation in which sufficient free space is required for the welding tool. A discontinuous course of the webs 5, 6 at this location has the effect that no exact and tight welding would be possible without destroying the webs 5, 6. For this reason, these existing discontinuities 24 are filled, upon assembly of the cooling device, with short webs 25 provided at the outer shell 14. Such a web 25 is visible in FIG. 5, in particular.

In the heat transfer unit of FIGS. 1 to 3, this problem has been solved differently by forming the regions needed as free space for the tool during welding between the upper part 18 and the lower part 19 of the heat transfer unit 1 in a continuous manner around the webs 5, 6 provided at the outer casing 2. This results in the undulated profile on the lower side, obvious from FIG. 2. This is advantageous in that friction stir welding can take place, for example, without interrupting the webs 5, 6, yet it is disadvantageous in that the through-flow cross section of the coolant passage 20 has to be maintained the same to avoid flow losses, so that an exact calculation of the existing surfaces has to be performed and has to be realized in the casting.

Further, it is obvious from FIGS. 4 and 5 that the cooling device is mounted to the actual cooling device by means of a top element 26 at which the exhaust gas inlet 8 and the exhaust gas outlet 9 are formed.

It is clear that both embodiments achieve a reliable meander-like positive circulating flow through the heat transfer unit 1, the coolant inlet and outlet 12, 13 being situated at the same axial end of the heat transfer unit 1. It should be obvious that an arrangement of the coolant inlet 12, as well as the exhaust gas inlet 8 and the coolant outlet 13 and the exhaust gas outlet 9 at axially opposite ends of the cooling device, with a meandering flow, is also possible, where merely one axial web would be required, from which axial web circumferential webs would have to extend alternately to either side and would each have to end before meeting the axial web again.

Another embodiment of a cooling device according to the invention is represented in FIG. 6. The coolant path is indicated by arrows. Elements or flows on the rear are indicated in broken lines.

Within this cooling device are two heat transfer units 27, 28 which are each completely passed by a positive circulating flow around their circumference. This flow is in the shape of an eight. For this purpose, each of the heat transfer units 27, 28 has an axial web 29, 30 extending from one axial end to the other. After assembly into the outer shell 31, both axial webs 29, 30 are located on opposite circumferential sides of the cooling device, so that the axial web 29 is indicated in broken lines.

A coolant inlet 32 is located on the side opposite with respect to the present view, from where the coolant flows in the circumferential direction about the first heat transfer unit 27. From here, the coolant flows on between the first heat transfer unit 27 and the second heat transfer unit 28, since the further path is interrupted by the web 30. The coolant flows on to the side of the cooling device averted from the present view and circumferentially around the second heat transfer unit 28. A lateral limitation of the passage 33 through which the coolant flows is formed by a circumferential web 34 extending around the entire heat transfer unit 27, and a circumferential web 35 that extends around the entire heat transfer unit 28, but ends before meeting the axial web 30. The flow in the circumferential direction thus ends at the axial web 30, where the coolant is deflected and flows on in the axial direction between the axial web 30 and the circumferential web 35. Then, the coolant is deflected again, since an axial flow is blocked by a web 36 extending circumferentially around the heat transfer unit 28. It flows around the second heat transfer unit 28, limited by the webs 35 and 36, and, due to the resistance formed by the second axial web 29, flows from there between the two heat transfer units 27, 28 to the side that corresponds to the present view.

In this manner, the further progress of the coolant proceeds past a web 37 at the first heat transfer unit 27, which ends shay of the web 30 on the rear side, to a coolant outlet 38. The necessary webs 42 between the two heat transfer units 27, 28 may optionally be formed at one or both het transfer units 27, 28. In the embodiment illustrated in FIGS. 6 and 7, the heat transfer units 27, 28 have a common casing 39ahich is closed on the opposite circumferential sides with a respective cover element 40, 41, so that the webs 42 between the heat transfer units 27, 28 are formed integrally with the casing 39.

When connecting the exhaust gas outlet of the first heat transfer unit 27 with the exhaust gas inlet of the second heat transfer unit 28, the exhaust gas cooling distance can thus be doubled without having to extend the axial structural length of a cooling device.

It should be evident that such a meandering positive circulating flow through a cooling device provides the advantages of an entirely freely selectable positioning of the coolant inlets and outlets 12, 13, 32, 38. Using this positive flow, a high efficiency of cooling devices thus structured is achieved. Assembly and manufacturing costs are significantly reduced as compared to known designs. In how far the existing webs are formed on the outer shell or on the outer casing of the heat transfer unit or are possibly configured as individual elements, remains free to choose. The outer shape of the hat transfer unit is also largely optional due to such a configuration of the coolant through-flow passages by the webs. 

1. A cooling device, comprising: a first outer shell in which at least one heat transfer unit is arranged that has an outer housing separating a jacket through which coolant flows and the jacket is formed between the first outer shell and the heat transfer unit from a passage formed in the heat transfer unit and through which fluid to be cooled flows; and webs arranged between the first outer shell and the outer housing of the heat transfer unit that define a passage in the jacket, through which coolant flows, wherein the heat transfer unit is made in a diecasting process and comprises an upper part and a cover-shaped lower part, wherein the upper part and the lower part are connected by welding, and said webs are arranged so that the heat transfer unit is passed by a meandering positive flow of coolant.
 2. The cooling device of claim 1, wherein a first axial web is arranged between the first outer shell and the heat transfer unit, and circumferential webs alternately extend from both sides of said axial web and around the heat transfer unit, and said circumferential webs end a distance shy of the axial web.
 3. The cooling device of claim 1, wherein two opposing axial webs are arranged between the first outer shell and the outer housing of the heat transfer unit, a first axial web of the two opposing axial webs ending shy of a last axial section of the cooling device, and circumferential webs extend around said heat transfer unit alternately from the first axial web and from a second axial web of the two opposing axial webs and each of the circumferential webs extends from both sides of a respective one of the opposing axial webs, and said circumferential webs end a distance shy of the respective other one of the two opposing axial webs, said distance corresponding to the distance between the circumferential webs.
 4. The cooling device of claim 1, wherein two heat transfer units are arranged in a second outer shell, and third axial webs and fourth circumferential webs are formed therebetween so that, in cross section, each of the heat transfer units are passed on all sides by a positive circulating flow of coolant.
 5. The cooling device of claim 4, wherein, in cross section, the circulating flow of coolant around the two heat transfer units is substantially in the shape of an eight.
 6. The cooling device of claim 4, wherein between the second outer shell and each of the two heat transfer units is arranged a respective third axial web, and these respective two third axial webs are provided at opposite circumferential sides of said passage, and fourth circumferential webs comprising fifth circumferential webs and sixth circumferential webs alternately extend around the heat transfer units from both sides of the third axial webs, wherein each fifth circumferential web ends a distance shy of one of the third axial webs and each sixth circumferential web ends a distance shy of the other one of the third axial webs.
 7. The cooling device of claim 1, wherein the webs are at least partly formed on the outer housing of the heat transfer unit.
 8. The cooling device of claim 1, wherein the first outer shell is at least bipartite and made by diecasting, and seventh webs are formed at least partly on an inner wall of the first outer shell.
 9. The cooling device of claim 1, wherein two opposing axial webs and two circumferential webs are formed substantially at the outer housing of the heat transfer unit and have discontinuities in a junction area between the upper part and the lower part, and which, in the assembled state, the discontinuities are filled by corresponding seventh webs of the first outer shell.
 10. The cooling device of claim 7, wherein, in cross section, two circumferential webs are continuous in a junction area between the upper part and the lower part of the heat transfer unit.
 11. The cooling device of claim 1, wherein the cooling device is an exhaust gas cooling device for an internal combustion engine.
 12. The cooling device of claim 1, wherein the upper part and the lower part are connected by friction stir welding.
 13. The cooling device of claim 2, wherein the axial web corresponds to the distance between said circumferential webs.
 14. The cooling device of claim 5, wherein between the second outer shell and each of the two heat transfer units is arranged a respective third axial web, and these respective two third axial webs are provided at opposite circumferential sides of said passage, and fourth circumferential webs comprising fifth circumferential webs and sixth circumferential webs alternately extend around the heat transfer units from both sides of the third axial webs, wherein each fifth circumferential web ends a distance shy of one of the third axial webs and each sixth circumferential web ends a distance shy of the other one of the third axial webs. 